Molecules is a leading international, peer-reviewed, open access journal of chemistry published semimonthly online by MDPI.

The modern concept of molecules can be traced back towards pre-scientific and Greek philosophers such as Leucippus and Democritus who argued that all the universe is composed of atoms and voids.

Mar 13, 2026 · Molecule, a group of two or more atoms that form the smallest identifiable unit into which a pure substance can be divided and still retain the composition and chemical properties of …

Sep 12, 2020 · Get the definition of a molecule. See examples of molecules and learn the different between a molecule and a compound.

Mar 25, 2026 · Molecules are formed during a chemical reaction when bonds are broken and reformed between atoms. This is in contrast to when a covalent compound undergoes a physical …

Feb 2, 2023 · All objects that we see around us are made of molecules. From living objects such as a plant or an animal, including humans, inanimate objects like a chair, table, wall, door, windows, …

PubChem is the world's largest collection of freely accessible chemical information. Search chemicals by name, molecular formula, structure, and other identifiers. Find chemical and physical properties, …

Jul 20, 2025 · Molecules are formed when two or more atoms are joined together by chemical bonds. For instance, a single oxygen atom (O) can exist, but it often bonds with another oxygen …

Learn about how different elements combine to form compounds with entirely new properties and how these compounds can exist as molecules or crystals.

Just as an atom is the simplest unit that has the fundamental chemical properties of an element, a molecule is the simplest unit that has the fundamental chemical properties of a covalent compound. …